Diameter ratio too large

Hi there,

I used your sonotrode calculator, it is very useful. I have an application whereby my 50W transducer have to have a horn of about 12mm radiator diameter. The calc says the diameter ratio is too large, could I make two steps like 45mm to 24mm and the next step is from 25 to 12mm? It finally would look like a full wave. Or should I have to go for exponential horn?

Thanks